This may surprise you, but there is no standard notation.
So I have no idea what those graphs are suppose to represent.
You have to define all you notation if you expect any help.

Okay, I'll try to help:

K2 is a complete graph of 2 vertices. A complete graph is a graph in which every two distinct vertices are joined by exactly one edge. The complete graph with n vertices is denoted by Kn.

C3 is a cycle of 3 vertices. The cycle graph with n vertices is denoted by Cn.

U means the "union" of the two. Which mean the two graphs are next too each other not connected at all. For two graphs with disjoint vertex sets V1 and V2 (and hence disjoint edge sets), their disjoint union is the graph U(V1 ∪ V2, E1 ∪ E2).[1] It is a commutative and associative operation (for unlabelled graphs).

X means Cartesian Product. The vertex set of G X H is the Cartesian product V(G) × V(H); and

any two vertices (u,u') and (v,v') are adjacent in G X H if and only if either